BTW, I installed it using yum on Fedora 9. Initially all other components (i.e. mysql, Apache, PHP, pcre) were installed using "yum -y install httpd" as instructed in the document I got from http://www.internetsecurityguru.com. However, It seems that some little components that PHP needed (e.g., PEAR, gd, libxml-2) were not installed using yum, so I then reinstalled PHP from source.

Following your suggestion, I first appended "index.html/php" in DirectoryIndex of /etc/httpd/conf/httpd.conf to no avail. I then attempted to re-compile/install PHP with the --with-httpd option, restarted the httpd service and opened https://snort_ip_address/base, but still got the same page of index of files and folders.

I am not familiar with Fedora, as I use Gentoo. As you have installed all the packages, you should have the file /etc/httpd/conf.d/php.conf. In this file add
DirectoryIndex index.php
if not in the file.
NOTE : Please note the difference here index.html/php :)

Then restart your httpd service.

Assuming all the above configuration is correct then in file /etc/base/base_conf.php

I got everything finally running as expected now after a fresh install on another Linux box. I figured it will take longer to sort everything to get a clue about the issue than to just start over. Thank you guys for all your inputs, that also help me through.